From Ohio History Central
The Hopewell Mound Group is a large Hopewell culture (100 BC-AD 500) ceremonial center located along the North Fork of Paint Creek in Ross County. According to the archaeologist N'omi Greber, the Hopewell Mound Group "contains, in both quality and quantity, the most striking total set of Hopewellian cultural remains" of any site in Ohio. The Hopewell culture is named for the Hopewell Mound Group, which was named for the family that owned the earthworks when the archaeologist Warren K. Moorehead explored the site in 1891 and 1892.
The Hopewell site is surrounded by a six-foot high, roughly rectangular earthen enclosure 2,800 feet long by 1,800 feet wide, known as the Great Enclosure. A perfectly square enclosure of 16 acres was attached to the eastern wall. Within the Great Enclosure there were other, smaller geometric enclosures and more than 30 mounds of various sizes and shapes. The largest of the mounds was a series of three conjoined mounds referred to as Mound 25. Mound 25 originally was 500 feet long, 180 feet wide, and 33 feet high making it as large as a three-story building spanning two city blocks.
The Hopewell Mound Group is listed on the National Register of Historic Places.